The present invention generally relates to electrical stimulation catheters typically utilized in treating the epidural space of a patient, in particular, a system for such treatment. More specifically, the invention relates to a catheter with flexible electrodes for providing electrical stimulation to the epidural space. The invention also relates to a device for securing-to-a patient a portion of an implanted epidural catheter and to a kit containing catheters and securing devices.
The application of electrical stimulation to the epidural space has proven to be effective in treating spinal pain. Single electrode spring wound catheters have been used with externally placed second electrodes. Multiple electrode catheters have also been used to provide electrical stimulation to the epidural space. The catheters are inserted into the epidural spaces through a hollow needle placed therein. Stimulation is provided by a power source that created a voltage differential across two electrodes which are electrically insulated from each other and positioned along the length of the catheter. Each of the two electrodes contact tissue or fluid in the epidural space of the patient to close an "electrical circuit". A liquid pain relieving agent, such as an anesthetic or narcotic may be injected through the catheter into the epidural space to provide further pain relief.
One spring wound catheter which has been successfully used for epidural stimulation is marketed under the tradename RACZ.TM. by Medical Evaluation Devices & Instruments Corporation of Gloversville, N.Y. However, this catheter has the drawback of requiring a second, external electrode. The construction of spring wound catheters in general is known from, for example, U.S. Pat. No. 3,757,768 to Kline, which discloses a spring guide catheter for intravenous feeding. The '768 catheter is composed of a helical spring covered with an inert halogenated hydrocarbon.
Prior art multiple electrode epidural catheters, such as those disclosed in U.S. Pat. No. 4,379,462 to Borkan and in U.S. Pat. No. 5,119,832 to Xavier have been constructed with rigid electrodes which hinder the process of feeding the catheter toward the epidural space. The Borkan '462 patent discloses a multi-electrode catheter which provides electrical stimulation to the spinal cord of a patient. In a preferred embodiment the '462 patent discloses electrodes which are composed of a rigid material, namely platinum rings. The Xavier '832 patent discloses a method for pain treatment which provides pulsing of electricity to the epidural space via a catheter with ring electrodes located on the external surface of the catheter. The '832 patent discloses as a preferred embodiment electrodes which are composed of rigid material, namely silver, gold or platinum. The method of the '832 patent also discloses delivery of a liquid pain relieving agent to the epidural space through the catheter.
Rigid electrodes are undesirable because, in general, they make the overall device less flexible and may become wedged in the sharp bends of the intricate passages through which a catheter must be fed. Prior art rigid electrodes may also present difficulties in fixation to the catheter. Glued connections can be unreliable and present quality control problems. Crimped connections tend to create sharp or rough spots on the electrodes that may catch on tissue or the insertion needle.
A further disadvantage of prior art stimulation or epidural catheters is the lack of early warning means to detect the presence of body fluids in the catheter lumen. For example, as the practitioner feeds the catheter toward the treatment site, the distal tip of the catheter may rupture a blood vessel. Prior art stimulation catheters such as those disclosed above, do not provide indication that a vessel has been ruptured until blood from the ruptured vessel has exited the proximal orifice of the catheter. As a result of the time required for blood to pass through the length of the catheter, the practitioner is not provided with a prompt indication of such a rupture.
Early warning means, often referred to as flashback devices, have been provided in specific configurations for other specific applications. For example, U.S. Pat. Nos. 4,710,173 to McFarlane and 4,317,445 to Robinson each disclose a flashback device which is a component of an intravenous catheter. The McFarlane '173 patent discloses a catheter insertion device in which a hollow needle is positioned within the lumen of the catheter, such that the distal end of the needle extends beyond the distal end of the catheter. When the needle penetrates a patient's vein, blood from the vein flows proximally within the needle to a portion of the device where a practitioner can observe the blood. This provides an indication that the needle is properly positioned within the patients vein. The Robinson '445 patent is essentially the same as the McFarlane '173 patent. However, the '445 invention indicates not only when the needle has entered the patient's vein, but also indicates when the cannula (catheter) has entered the patient's vein. A dead space annulus between the exterior of the needle and the interior of the cannula receives blood when the cannula has entered a vein. This blood flows proximally within the dead space annulus of the cannula to a portion of the device where a practitioner can observe the blood, thereby indicating that the cannula is properly positioned within the patient's vein.
Once an epidural catheter has been implanted in a patient and positioned to provide optimal treatment, it is desirable to leave the catheter implanted such that it does not need to be reinserted for future treatments. Allowing the catheter to remain implanted in the patient creates a risk that the catheter may be inadvertently dislodged from the position of optimal treatment or completely dislodged from the patient. Again, the prior art has failed to provide suitable means for easily securing a long term stimulation catheter and preventing it from becoming dislodged from the epidural space or completely dislodged from the patient.